1. Field of the Invention
This invention relates to a novel mold for cast-molding a slip, and a method for producing the mold. More particularly, this invention relates to the casting mold having precise dimensions, good durability, uniform deposition properties, and good demolding properties. The molds of the present invention are useful for producing cast-molded articles from a ceramic slip, for obtaining sanitary ware, pottery ware, other ceramic products, etc.
2. Prior Art
Conventional methods for casting slips comprise, for example, filling the mod cavity of a divisible gypsum mold with a slip, and depositing the slip onto the surface of the gypsum mold by the action of gypsum in absorbing water from the slip. In a mechanical cast-molding process, such operations are efficiently carried out by pressurizing the slip to promote the dehydration and deposition of the slip.
In view of durability of a casting mold, it has been known to use the casting mold composed of a porous synthetic resin. It has been needed, however, to install water-drainage conduits in such a synthetic resin mold from viewpoint of safe demolding and relatively uniform deposition, because open-cell porosity of a resin mold was usually not uniform.
In general, the defects of such synthetic resin molds have been deterioration in precise dimensions and shapes of the mold because of large curing shrinkage during production of such synthetic resin molds. In this connection, a porous epoxy resin molded product and a mold composed thereof are known, which are produced from an epoxy compound, a hardener compound, fillers, mixtures of suitable non-ionic emulsifiers, etc. (Laid-open European Patent Application No. 0194757). The Laid-open Patent Specification, however, fails to note serious problems such as formation of an emulsifier-based viscous substance hardly soluble in cool water, remaining in the preliminarily cured epoxy resin, and elution of the viscous substance with a solvent.
The present inventors have noted that formation of the uniform fine open-cell structure of cured resins is hindered in the course of curing a synthetic resin emulsion material containing a non-ionic emulsifier, because an emulsifier-based viscous substance hardly soluble in cool water remains in the cured resin and is then solidified. Incidentally, the viscous substances seem to be a dense mixture of the emulsifier and water, a reaction mixture of the emulsifier and a polymerizable material, and/or a mixture of the emulsifier and a low-polymer resin.
The present inventors have solved the above mentioned problems by substantially eluting the emulsifier-based viscous substance with a large amount of a solvent such as warm water containing an alcohol. Moreover, the present inventors have also found that installation of water-drainage conduits in the casting mold produced from an emulsifier-containing resin material should be avoided, because a solvent for eluting the emulsifier based viscous substance is apt to flow towards the conduits and thus the non-uniform elution of the viscous substance results in non-uniform open-cell structures of the synthetic resin mold.